I get this error: "AttributeError: 'NoneType' object has no attribute 'seek'"

Hi

I'm trying to delete adverts from a film recorded in my TDT in mpg format and pitivi outputs this error: "AttributeError: 'NoneType' object has no attribute 'seek'". When I try to seek it shows this error:

ERROR 09:01:49 pipeline pitivi+utils+pipeline+pipeline0 _async_done_not_received_cb: we didn't get async done, this is a bug (../../usr/lib/pitivi/python/pitivi/utils/pipeline.py:299)